SOT: The truth about Corvair engines, Nothing but the facts and experience, please Options

[Dr Evil]

There has been lots of interest in the corvair power plant over the years as a possible source of cheap HP for many vehicles. There are used in experimental aviation, dune buggies, buses (such as mine), and in place of many other air cooled VW power plants. They are fairly cheap to buy and build, very easy to build and maintain, and plentiful with readily available parts from several suppliers.

The main divide in the corvair engine line took place in 1965 when the displacement of the engine was moved to 2.7L and was offered in a NA 110HP, NA140HP, turbo 150HP and turbo 180HP. The only differences in the long block between these engines are the nitrided crank found in all but the 110HP, and the heads: 110 had one single barrel on each head, the 140 had 2 with one acting as primary and one as secondary. The turbos had a single barrel blow through setup.

The heads are the major limiting factor in the design. They are not built in an intuitive way and rob much hp. The 140 head had bigger valves, but like its 2.0L TIV analog, would drop valve seats due to the limited amount of material between the seats in the head, and the inability of larger seats to shed heat as well as smaller seats. This can, and has been overcome by those who have been rebuilding these heads fro decades by making sure the crush tolerance on the seats are correct, and staking the seats in place.

Currently, you can get a set of rebuilt, 140hp larger valved heads, with new hardware and no core for about $1200 from Corvair Ranch in Gettysburg, PA. I bought a set that was rebuilt and had the plenums taken off for tri porting for $1500 shipped off of ebay from Starr Cooke in El Cajon, CA, another well known Corvair entity.

Modified with plenum removed for individual runners:


The above uses an adapter that allows the placement of Weber triples. My set came with this adapter.

Here is a head with a stock plenum, modified with bungs for FI. This is a 140 head as it has two carb bases on it:


Standard engine:


One of the cool things that many ACVW folks like is that the corvair engine has stock hydraulic lifters on it that use standard lifter, push rod, and rocker parts from Chevy. Easy and cheap to obtain.

Another great feature that I like over ACVW is the box design on the case. The top and bottom come off and allow for any maintenance. Swapping rods, bearings, what ever, is easy.

[jk76.914]

Nice summary- I offer a couple of clarifications-

The main divide in the corvair engine line took place in 1965 when the displacement of the engine was moved to 2.7L and was offered in a NA 110HP, NA140HP, turbo 150HP and turbo 180HP. The only differences in the long block between these engines are the nitrided crank found in all but the 110HP, and the heads: 110 had one single barrel on each head, the 140 had 2 with one acting as primary and one as secondary. The turbos had a single barrel blow through setup.

The heads are the major limiting factor in the design. They are not built in an intuitive way and rob much hp. The 140 head had bigger valves, but like its 2.0L TIV analog, would drop valve seats due to the limited amount of material between the seats in the head, and the inability of larger seats to shed heat as well as smaller seats. This can, and has been overcome by those who have been rebuilding these heads fro decades by making sure the crush tolerance on the seats are correct, and staking the seats in place.

Currently, you can get a set of rebuilt, 140hp larger valved heads, with new hardware and no core for about $1200 from Corvair Ranch in Gettysburg, PA. I bought a set that was rebuilt and had the plenums taken off for tri porting for $1500 shipped off of ebay from Starr Cooke in El Cajon, CA, another well known Corvair entity.

One of the cool things that many ACVW folks like is that the corvair engine has stock hydraulic lifters on it that use standard lifter, push rod, and rocker parts from Chevy. Easy and cheap to obtain.

Another great feature that I like over ACVW is the box design on the case. The top and bottom come off and allow for any maintenance. Swapping rods, bearings, what ever, is easy.

The original 1960 was 140 cu.in. '61-63 they went to 145 with a bore increase, and the move to 164 (2.7L) was a stroke increase in '64, not '65. If you're building a '64 engine, there are some cylinder barrel and head differences from '65 and up that you need to know about...

There was also a base engine, 95 hp, below the 110 for all years. It used the non-nitrided crank along with the 110hp. But even in this form, it was forged steel, not cast.

The turbo came out in 1962 at 150 hp. And didn't go to 180 hp until '65. The '64 turbo was still rated at 150 hp even though it was on the bigger 164 cu. in. engine. All turbos were draw-through, not blow-through, single barrel Carter YH side draft carbs. Interestingly, three of these carbs were used on the original 1953 Corvette blue flame six. There was significant turbo lag. Chevy really simplified the installation though, by using a pressure retard on the distributor instead of a vacuum advance. Static timing was 24 degrees BTDC, which advanced centrifugally and then retarded under pressure. My own '63 Sypder convertible started showing positive boost at around 2500 rpm, and topped out at 10 PSI (20" Hg) by maybe 4200. I actually liked the turbo lag. For freeway passing, you could feel yourself pressing into the seat as the vac/pressure guage climbed above zero.

I don't recall any issues with dropped seats except with the big valve 140 heads.

Lifters and rockers were based on Chevy desings, but different. Pushrods were unique as they have a side bleed hole to lubricate the rocker boxes. This is necessary because the hydraulic lifters operate with zero lash, which shuts off much of the oil flow to the head. I actually am running Corvair pushrods in my T4 hydro engine for that reason- stock length fit perfecdt!

My own three Corvairs (110hp-'64, 140hp- '65, and 150 hp- '63) were indestructible, I'm convinced. Totally reliable, easy to maintain, and on and on.